Optical apparatus for continuous television film projection system

ABSTRACT

Two partially light transmissive and partially light reflective light-forwarding devices in the main optical path between the film and a camera tube are rotated so that a light replica of a film frame is transmitted through the devices when the frame is in the center of the film gate and other light replicas are reflected from one device to the other by way of stationary reflectors on opposite sides of the main optical path and thence to the camera tube when the frame has just completely entered and is about to leave the gate, respectively.

United States Patent Boltz, Jr.

[541 OPTICAL APPARATUS FOR CONTINUOUS TELEVISION FILM [451 July 25,1972

Primary Examiner-Robert L. Griffin Assistant Examiner-George G. StellarPROJECTION SYSTEM Attorney-Eugene M. Whitacre [72] Inventor: Charles D.Boltz, Jr., Greenwood, Ind.

[73] Assignee: RCA Corporation [57] ABSTRACT Filed: March 1971 Twopartially light transmissive and partially light reflective liht-forwardin devices in the main 0 tical ath between the 21 A LN 1200758 g P P l 1 pp 0 film and a camera tube are rotated so that a lightreplica of a film frame is transmitted through the devices when theframe US. Cl- 28, is in the center of the gate and other replicas are[51] Int. Cl ..I-I04n 1/04, 60% 41/02 fl t d f one device to the otherby way f stationary [58] Fleld of Search ..l78/6.7 A, 7.2,DIG. 28;reflectors on opposite Sides of the main optical path and 352/105 1 ll l12 thence to the camera tube when the frame has just completely [56]References Cited entered and is about to leave the gate, respectively.

UNITED STATES PATENTS 10 Claims 5 Drawing Figures 3,584,148 6/1971 Flory..l78/DIG. 28

f/Wflflfl/M/P .4 -39 1 0%? [55/1 17 7 /7070 flffffiO/i 71676657?67/?60/7 W MW/W005 38 Z/M/PPfl/ff/r 50/72) amt/kw 554/? 304 PATENTEDJuL25 I972 A sum 2 BF 4 A VENTOR. Charles D. Boltz,.lr. BY

A TTOR/VE'Y PAIENTEDJUL25 1972 SHEET 3 OF 4 I N VEN TOR. Charles B.Boltz, in B Y x NQQQM w m A T TOR/V5 Y OPTICAL APPARATUS FOR CONTINUOUSTELEVISION FILM PROJECTION SYSTEM BACKGROUND OF THE INVENTION Intelevision systems in which a motion picture film is projected onto thephotosensitive electrode of a camera tube that is scanned by an electronbeam to generate video signals representative of the informationrecorded in the image-bearing film frames, one of the disadvantages ofan intermittent film transport mechanism is the attendant acoustic noisefactor. Such unwanted acoustic output of a conventional intermittentfilm transport mechanism would be particularly objectionable in anysystem intended for home use to display regular 8 millimeter or super 8"millimeter film, for example, on a conventional television receiver.Also, a considerable strain is placed upon the film which tends todistort and/or to tear out the sprocket holes and to render moredifficult the realization of sufficiently uniform film motion for goodsound pickup and reproduction from films having sound tracks.

Continuous motion film transport mechanisms are not subject to suchdescribed difficulties encountered with intermittent film transportapparatus, but have their own peculiar problems. Where non-storage typesof television camera tubes have been employed, complex and difficult tocontrol optical compensating apparatus has been needed to maintain alight replica of each film frame substantially stationary on thephotosensitive camera tube electrode during a complete vertical scanningperiod. Where storage types of camera tubes are used, however, anintense light replica of a film frame may be projected onto thephotosensitive camera tube electrode in the blanking interval betweenvertical scanning periods. Because the frame rate of the motion picturefilm generally is slower than the television scanning rate it isnecessary to project a plurality of light replicas of each film frameonto the camera tube electrode for scansion a plurality of times. Agiven film frame, however, will be in different positions in the filmgate when the light replica projections are to be made and it isnecessary that all projected light replicas be accurately registered onthe photosensitive electrode of the camera tube in order to developproperly representative video signals.

Apparatus of the latter type which has been successively operated isdisclosed in the copending application of Robert E. Flory, Ser. No.857,1 15, filed Sept. 1 l, 1969 and entitled Motion CompensatingApparatus for Continuous Television Film Projection System," now US.Pat. No. 3,584,148 issued J une 8, 197 1. Such apparatus includes arotating mirror system disposed in the optical path between the film andthe camera to compensate for the film motion between successivestroboscopic light flashes. The strobe lamp produces light of one colorand is triggered into operation in response to the projection of lightof another color through the sprocket holes of the film when therotating mirror system is in the proper positions to project lightreplicas of the moving film onto the camera tube. The sprocket holelight and that constituting the film light replicas traverse that partof the optical system including the rotating mirror system in oppositedirections and are separated by dichroic mirrors to perform theirrespective functions.

SUMMARY OF THE INVENTION The apparatus of the present invention, whichrequires no dichroic mirrors, includes two continuously movinglight-forwarding devices in a main optical path between the continuouslymoving film and the camera tube, each device being partly lighttransmissive and partly light reflective. It also includes at least onestationary light-reflecting member in a branch optical path at one sideof the main optical path. When a given film frame is in one position inthe film gate, light therefrom is transmitted through thelight-forwarding devices directly along the main optical path to thecamera tube. When the frame is in another position in the gate, lighttherefrom is reflected from a first one of the light-forwarding devicesalong a branch optical path to the stationary light-reflecting memberand from it back to the second light-forwarding device which reflects itto the camera tube in register with the first light replica. The opticalapparatus of the invention may also include another stationarylight-reflecting member in a second branch optical path on the otherside of the main optical path so that, when the film frame is in a thirdposition in the gate, a light replica of the frame is reflected from thefirst light-forwarding device to the second stationary reflecting memberand thence to the second light-forwarding device for further reflectionto the camera tube in register with the other two light replicas of thegiven frame. The light replicas are produced by a strobe lamp which istriggered in response to the detection of light from a continuous sourcethrough the sprocket holes of the film when it is in the properpositions in the film gate to have the strobe light projected by theoptical system to the camera tube.

For a more specific disclosure of the invention reference may be had tothe following detailed description of an illustrative embodiment thereofwhich is given in conjunction with the accompanying drawings, of which:

FIG. 1 is a fragmentary section of a typical motion picture film whichmay be used with the invention;

FIG. 2 is a diagrammatic representation of a television film projectionsystem in which a presently preferred form of the optical systemcomprising the invention is embodied;

FIG. 3 is a diagrammatic showing of the operation of the opticalapparatus of the invention when a given film has just entered the filmgate;

FIG. 4 is a diagrammatic illustration of the operation of the opticalapparatus embodying the invention when the given film frame is centeredin the gate; and

FIG. 5 is a diagrammatic disclosure of the operation of the film motioncompensating apparatus of the invention when the given film frame isabout to leave the gate.

DESCRIPTION OF THE INVENTION In FIG. I an example of the type of film 11with which the invention may be used has a series of image-bearingframes 12, [2a, 1212, etc., and a series of sprocket holes 13, 13a, 13b,etc., located in a marginal strip 14 adjacent the frames 12, etc. In theillustrated form of the invention the sprocket holes 13, etc., functionas the frame position-identifying indicia in a manner to be describedsubsequently. It should be recognized that additional indicia may alsobe provided.

In FIG. 2 the motion picture film 11 is moved downwardly continuouslythrough a film gate 15 in the direction of the arrow 16 by anyconventional film transport apparatus which, in this case, includes asprocket wheel 17 that is rotated in the direction of the arrow 18 by asynchronous motor 19 through a reduction gear 21. The motor 19 isenergized by a connection to a source of alternating current atterminals 22.

The projection apparatus includes a stroboscopic light source, such asxenon flash lamp 23 which, when actuated, produces 5 short intense flashof light that is directed along a main optical path 24 to thephotosensitive electrode 25 of a vidicon type of camera tube 26. Betweenthe lamp 23 and the camera tube electrode 25 this main optical path 24includes a collimating lens system 27, the film ll, film motioncompensating apparatus (comprising a pair of tandemly arranged movablelight-forwarding devices 28 and 29), a path length correcting lens 31and a relay lens system 32. The film motion compensating apparatus alsoincludes two stationary lightreflecting members 33-33a and 34-34alocated respectively in first and second branch optical paths onopposite sides of the main optical path 24.

A continuous light source such as a lamp 35 which is energized by apower supply 36 is located adjacent the main optical path 24 in aposition to direct light substantially only through the sprocket holes13, etc., the film motion compensating apparatus (including thelight-forwarding devices 28-29 and the light-reflecting members 33-34)and to a small sprocket hole light-intercepting mirror 37. Lighttransmitted through the sprocket holes 13, etc., and the film motioncompensating apparatus is reflected from the mirror 37 and is directedthrough a sprocket hole light aperture 38 to a photodetector 39. Inresponse to a pulse of sprocket hole light the photodetector 39 developsa triggering pulse which is impressed upon the trigger circuit and powersupply 41 for the momentary actuation of the stroboscopic flash lamp 23.

The light-forwarding devices 28 and 29 are mounted on respectiveturntables 42 and 43, the latter of which is rotated in the direction ofthe arrow 44 by the synchronous motor 19 through a reduction gear 45.The respective turn-tables 42 and 43 are provided with intermeshingperipheral gear teeth 46 and 47 so that the turntable 42 is rotated inthe direction of the arrow 48. The light-forwarding devices 28 and 29have respective reflecting surfaces 49 and 51 which reflectapproximately one-half of the light from the lamps 23 and 35 strikingthem, the other half of the impinging light being transmitted throughthe devices. Opaque shutters 52-53 and 54-55 are provided respectivelywith the light-forwarding devices 28 and 29 to prevent the transmissionof light along the entire length of the main optical path 24 at certainstages of the operation of the film motion compensating apparatus to bedescribed presently.

In the film projection system of FIG. 2 the film 11 is continuouslyadvanced through the gate 15 at the rate of 20 frames per second and thephotosensitive electrode 25 of the camera tube 26 is scanned by anelectron beam (not shown) under the control of a deflection yoke 56,energized by a conventional deflection wave generator 57 at, forexample, the United States standard television rate of 60 fields persecond. Hence, three light replicas of each image-bearing frame of thefilm are projected during vertical blanking intervals successively ontothe camera tube electrode 25 for respective scansions during threesuccessive television field periods. In order to accomplish suchprojection the sprocket wheel 17, which is provided with sprocket holeengaging teeth 58, is rotated at 120 R.P.M. and the light-forwardingdevices 28 and 29 are rotated at L200 R.P.M. In the followingdescription of the operation of the film motion compensating apparatusof the invention the passage of a typical film frame 12 through the gatewill be discussed. In such apparatus the gate has a height that is l ofthe height or vertical dimension of a film frame.

In FIG. 3 the optical film motion compensating apparatus is shown in itsproper position to project upon the photosensitive electrode 25 of thecamera tube 26 a typical film frame 12 just as it is transported to bewholly within the gate 15. This instant occurs during a verticalblanking interval and at the same time that the light-forwarding devices28 and 29 are in the positions shown. The semi-reflecting surfaces 49and 51 of the respective devices are facing upwardly at substantially120 angles to the main optical path 24 so that light through thesprocket hole 13, that is transmitted along the broken line path 59above and parallel to the main optical path 24, is reflected along abroken line segment 61a of a first branch optical path to the stationarylight-reflecting member 33-33:! and thence along a broken line segment61b of the first branch optical path to the semi-reflecting surface 51of the light-forwarding device 29. The reflector surfaces of thelight-reflecting member 3333a face one another at 60 angles to the mainoptical path 24 and the member is positioned slightly on the camera tube26 side of the median line 62 between the lightforwarding devices 28 and29. By such an arrangement the branch optical path segment 61b meets thesemi-reflecting surface 51 at the main optical path 24. Thus, from thelightforwarding device 29 the sprocket hole light follows an opticalpath 63 coinciding with the main optical path 24 to the mirror 37 fromwhich it is reflected along the broken line path 64 for transmissionthrough the sprocket hole aperture 38 to the photodetector 39. Theresultant actuation of the stroboscopic lamp 23 causes the projectionupon the photosensitive electrode 25 of the camera tube 26 of amomentary light replica of the film frame 12 along an optical routecentered about the broken line optical path 59-61a-6lb-63 and indicatedby the solid lines 65-65a-65b-65c.

Any light from either the image-bearing film frame 12 or the sprockethole 13 that is transmitted through the light-forwarding device 28because of its semi-transparency is prevented from reaching thelight-forwarding device 29 by the opaque shutters 53 and 55. It will beobserved that the single shutter 53 would suffice for such purpose butit is advantageous to fabricate both light-forwarding members 28 and 29alike so that manufacturing economies may be realized and so that thetwo members may be interchangeably used in the system.

FIG. 4 shows the respective positions of the typical film frame 12 andthe light-forwarding devices 28 and 29 one-sixtieth of a second laterduring the next vertical blanking interval. The frame 12 is centeredvertically in the gate 15 and the light-forwarding devices 28 and 29 areat right angles to the main optical path 24 with their respectivereflecting surfaces 49 and 51 facing one another. Light from the lamp 35through the sprocket hole 13 follows the broken line path 66, whichcoincides vertically with the main optical path 24, through thelight-forwarding device 28, along the broken line path 67, and throughthe path length correcting lens 31 and the light-forwarding device 29from which it emerges along the broken line path 63 for reflection bythe mirror 37 along the broken line path 64 to the photodetector 39. Ina similar manner the momentary light replica of the frame 12 produced bythe ac tuation of the flash lamp 23 follows an optical route indicatedby the solid lines 68-69-650 through the light-forwarding devices 28 and29 and the lenses 31 and 32 to the photosensitive electrode 25 of thecamera tube 26. Because the optical route segment 65c of FIG. 4 isidentical to the corresponding route 65c of FIG. 3 the light replica ofthe frame 12 are projecte'd onto the camera tube 26 in identicalpositions. The optical path length correcting lens 31 effectivelylengthens the respective optical paths 67 and 69 to be substantiallyequivalent optically to the branch paths 6la-6b and 65a-65b of FIG. 3.

In FIG. 5 the typical film frame 12 is shown in its positionone-sixtieth of a second later during the next vertical blankinginterval just as it is about to be transported out of the gate 15. Thelight-forwarding devices 28 and 29 are at l20 angles to the main opticalpath 24 with their respective reflecting surfaces 49 and 51 facingdownwardly. Light from the lamp 35 that is transmitted through thesprocket hole I3 follows a broken line path 71 which is parallel to andbelow the main optical path 24 and is reflected by the surface 49 alonga second branch optical path 72a to the stationary reflecting member34-34a. The reflectors 34 and 340 face one another at 60 angles to themain optical path 24 and the member is located slightly on the cameratube 26 side of the median line 62. Thus, the stationary reflectingmember 34-34a redirects the sprocket hole light along the broken linesegment 72b of the second branch optical path to the reflecting surfaceof the light-forwarding device 29, from which it is reflected along thepath 63 followed by similar light in the two previously describedoperating stages of the film motion compensating apparatus of theinvention shown in FIGS. 3 and 4. Also, in a manner similar to thatdescribed with reference to FIG. 3 the light replica of the film frame12 follows the route depicted by the solid lines 73 and is reflectedfrom the light-forwarding device 28 along the solid lines 73a to thestationary reflecting member 34-34a and from it along the solid lines73b to the light-forwarding device 29 from which it is projected by thelens 32 along the solid lines 650 to the camera tube 26. Again it isseen that this light replica of the frame 12 impinges upon the cameratube photosensitive electrode 25 in precise register with the lightreplicas of this frame produced by the apparatus of the invention in thepositions shown in FIGS. 3 and 4. In the FIG. 5 position thetransmission of light along the entire length of the main optical path24 is prevented by the opaque shutters 52 and 54.

It is to be noted that only the light transmitted through the sprockethole 13 which emerges from the light-forwarding device 29 along theoptical path 63 is effective to cause the photodetector 39 to actuatethe trigger circuit 41 for the stroboscopic flash lamp 23. This isinsured by the respective positions of the mirror 37 and the sprockethole light aperture 38. As the film 11 and the light-forwarding devices28 and 29 are being moved from one to another of the positions shown inFIGS. 3, 4 and 5 sprocket hole light is being forwarded in the generaldirection of the camera tube 26 by the film motion compensatingapparatus of the invention, either by direct transmission through thedevices 28 and 29 or by reflection from the stationary reflectingmembers 33-330 and 34-340. It is the function of the aperture 38 totransmit to the photodetector 39 only that sprocket hole light thatreaches the mirror 37 by way of the optical path denoted by the brokenline 63. All other light is excluded from the aperture 38 so that thephotodetector 39, and hence the stroboscopic lamp 23, respond only whenthe film frame 12 and the film motion compensating apparatus are in oneof the positions shown in FIGS. 3,4 and 5.

An important advantage of the film motion compensating apparatus of theinvention is that the components thereof need not be fabricated with anexceedingly high degree of precision. Instead, the high precisionrequired in the operation of the apparatus is easily attainable bysuitable adjustment of the components after assembly.

As used in the foregoing specification and in the following claims, theterm image-bearing frame is defined as one in which there is aphotographic record of an object or scene such as a true positive ornegative, black and white or color image or an encoded representationthereof as, for example, in systems such as in U. S. Pat. No. 2,733,291granted Jan. 31, 1956 to R. D. Kell and in U. S. Pat. No. 3,378,633granted Apr. 16, 1968 to A. Macovski where the component colorinformation is spatially encoded on black and white film.

In such patented systems the color encoding is in the form of a finestructure of color representative strips which are oriented verticallyand/or at one or more angles to the horizontal dimension of the filmframes. The projection of the light replicas of such a strip structureonto the photosensitive camera tube electrode 25 and its scansion by anelectron beam develop video signals in the output of the camera tube 25which include the component color information as amplitude modulationsof a plurality of relatively high frequency carrier waves.

What is claimed is:

I. In a television film projection system, motion compensating apparatusfor precisely positioning in substantially the same place on a storagetype photosensitive electrode of a camera tube during respectivevertical blanking intervals a plurality of momentary light replicas ofeach of a series of image-bearing frames of a motion picture film beingcontinuously moved in the longitudinal dimension thereof past a filmgate, said light replicas being produced by light from a stroboscopiclight source momentarily actuated by the detection of frameposition-identifying indicia in a marginal strip of said film adjacenteach of said image-bearing frames, said film motion compensatingapparatus comprising:

first and second lightforwarding devices in a main optical path betweensaid film and said camera tube, each of said devices being partly lighttransmissive and partly light reflective;

at least a first stationary light-reflecting member positioned in afirst branch optical path on one side of said main optical path; and

means for continuously moving said first and second lightforwardingdevices so as to transmit light from a given film frame in a firstposition in said gate directly along the entire length of said mainoptical path to said camera tube, and to reflect light form said givenfilm frame in a second position in said gate from said firstlight-forwarding device to said first light-reflecting member, andthence to said second light-forwarding for reflection therefrom to saidcamera tube.

2. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim I, wherein:

a second stationary light-reflecting member is positioned in a secondbranch optical path on the opposite side of said main optical path fromsaid first branch optical path; and

said first and second light-forwarding devices being movable to reflectlight from said given film frame in a third position in said gate fromsaid first light-forwarding device to said second light-reflectingmember, and thence to said second light-forwarding device for reflectiontherefrom to said camera tube.

3. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 2, wherein:

said first and second light-forwarding devices are tandemly arranged insaid main optical path and are oppositely rotatable about respectiveaxes parallel to the transverse dimension of said film.

4. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 3, wherein;

each of said first and second light-reflecting members comprises firstand second mirrors angularly positioned relative to one another and tosaid main optical path so that said first mirror receives lightreflected from said first light-forwarding device and reflects it tosaid second mirror which reflects it to said second light-forwardingdevice.

5. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 4, wherein:

each of said first and second light-forwarding devices includes lightshutters positioned so as to prevent light from said given film framefrom being transmitted directly to said camera tube when saidlight-forwarding devices are operative to reflect light from said givenfilm frame in said second and third positions thereof in said gate.

6. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 5, wherein:

said main optical path includes a lens to compensate for the longerlight paths from said film to said camera tube through said first andsecond branch optical paths.

7. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 6, wherein:

said first and second light-forwarding devices are geared together andare driven to make one revolution for the travel of each film framethrough said gate.

8. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 7, wherein:

said film frame position-identifying indicia comprise one sprocket holefor each image-bearing frame;

a source of continuous illumination for said sprocket holes;

and

means responsive to light through each of said sprocket holes when eachof said film frames is in said first, second and third positions in saidgate to momentarily actuate said stroboscopic light source to producelight replicas of said image-bearing film frames for forwarding to saidcamera tube.

9. In a continuously moving television film projection system, filmmotion compensating apparatus as defined in claim 8, wherein:

said sprocket hole light responsive means includes a sprocket holelight-intercepting mirror positioned between said light-forwardingdevices and said camera tube to divert said sprocket hole light to aphotodetector for the production of a triggering pulse to actuate saidstroboscopic light source.

photodetector only when said light-forwarding devices are operative toforward light from said film frame in any of said first, second andthird positions thereof in said gate.

1. In a television film projection system, motion compensating apparatusfor precisely positioning in substantially the same place on a storagetype photosensitive electrode of a camera tube during respectivevertical blanking intervals a plurality of momentary light replicas ofeach of a series of image-bearing frames of a motion picture film beingcontinuously moved in the longitudinal dimension thereof past a filmgate, said light replicas being produced by light from a stroboscopiclight source momentarily actuated by the detection of framepositionidentifying indicia in a marginal strip of said film adjacenteach of said image-bearing frames, said film motion compensatingapparatus comprising: first and second light-forwarding devices in amain optical path between said film and said camera tube, each of saiddevices being partly light transmissive and partly light reflective; atleast a first stationary light-reflecting member positioned in a firstbranch optical path on one side of said main optical path; and means forcontinuously moving said first and second lightforwarding devices so asto transmit light from a given film frame in a first position in saidgate directly along the entire length of said main optical path to saidcamera tube, and to reflect light form said given film frame in a secondposition in said gate from said first light-forwarding device to saidfirst light-reflecting member, and thence to said secondlight-forwarding for reflection therefrom to said camera tube.
 2. In acontinuously moving television film projection system, film motioncompensating apparatus as defined in claim 1, wherein: a secondstationary light-reflecting member is positioned in a second branchoptical path on the opposite side of said main optical path from saidfirst branch optical path; and said first and second light-forwardingdevices being movable to reflect light from said given film frame in athird position in said gate from said first light-forwarding device tosaid second light-reflecting member, and thence to said secondlight-forwarding device for reflection therefrom to said camera tube. 3.In a continuously moving television film projection system, film motioncompensating apparatus as defined in claim 2, wherein: said first andsecond light-forwarding devices are tandemly arranged in said mainoptical path and are oppositely rotatable about respective axes parallelto the transverse dimension of said film.
 4. In a continuously movingtelevision film projection system, film motion compensating apparatus asdefined in claim 3, wherein; each of said first and secondlight-reflecting members comprises first and second mirrors angularlypositioned relative to one another and to said main optical path so thatsaid first mirror receives light reflected from said firstlight-forwarding device and reflects it to said second mirror whichreflects it to said second light-forwarding device.
 5. In a continuouslymoving television film projection system, film motion compensatingapparatus as defined in clAim 4, wherein: each of said first and secondlight-forwarding devices includes light shutters positioned so as toprevent light from said given film frame from being transmitted directlyto said camera tube when said light-forwarding devices are operative toreflect light from said given film frame in said second and thirdpositions thereof in said gate.
 6. In a continuously moving televisionfilm projection system, film motion compensating apparatus as defined inclaim 5, wherein: said main optical path includes a lens to compensatefor the longer light paths from said film to said camera tube throughsaid first and second branch optical paths.
 7. In a continuously movingtelevision film projection system, film motion compensating apparatus asdefined in claim 6, wherein: said first and second light-forwardingdevices are geared together and are driven to make one revolution forthe travel of each film frame through said gate.
 8. In a continuouslymoving television film projection system, film motion compensatingapparatus as defined in claim 7, wherein: said film frameposition-identifying indicia comprise one sprocket hole for eachimage-bearing frame; a source of continuous illumination for saidsprocket holes; and means responsive to light through each of saidsprocket holes when each of said film frames is in said first, secondand third positions in said gate to momentarily actuate saidstroboscopic light source to produce light replicas of saidimage-bearing film frames for forwarding to said camera tube.
 9. In acontinuously moving television film projection system, film motioncompensating apparatus as defined in claim 8, wherein: said sprockethole light responsive means includes a sprocket hole light-interceptingmirror positioned between said light-forwarding devices and said cameratube to divert said sprocket hole light to a photodetector for theproduction of a triggering pulse to actuate said stroboscopic lightsource.
 10. In a continuously moving television film projection system,film motion compensating apparatus as defined in claim 9 wherein: saidsprocket hole light responsive means also includes an aperturepositioned between said intercepting mirror and said photodetector toadmit sprocket hole light to said photodetector only when saidlight-forwarding devices are operative to forward light from said filmframe in any of said first, second and third positions thereof in saidgate.